1. Field of the Invention
This invention relates to a temperature pattern measuring method for obtaining the distribution of surface temperatures over the surface of an object, and to a device for carrying out the method.
2. Description of the Prior Art
Generally, temperature pattern measuring methods have widely employed an infrared ray system which picks up by an infrared ray detection element in a two-dimensional pattern the optical energy of infrared rays emitted from an object the surface temperature distribution of which is to be measured, and scans the two-dimensional pattern and produces and displays a temperature pattern of the surface area of the object, for example, graphically on a cathode-ray tube (CRT). A measuring method using an infrared ray system, however, is inadequate for an object which changes temperature rapidly because two or more seconds are required for scanning to produce one picture. Moreover, the infrared rays picked up as representing temperature information are apt to be affected by the atmosphere surrounding the light propagation path due to the existence of vapor or dust, thereby lowering the sensitivity and accuracy. It is impossible in practice to avoid the influence of the surrounding atmosphere by the use of an image guide, because the attenuation of the quantity of light within the image guide is large in the infrared ray wavelength range. Furthermore, the minimum visual field within which measurement can be carried out is a 10 to 20 centimeter-angle, so that a temperature pattern in a smaller area cannot be measured. Hence, the infrared ray system cannot be used for measurement of the temperature pattern of an object, such as a slab in a continuous casting process in a steel mill or an electrically seamed steel pipe which is being welded, which is in a bad atmosphere having a lot of vapour or dust and which is undergoing a large temperature change. Moreover, it is impossible for this system to measure the temperature pattern in a small area, such as a heated portion of the edge of an electrically seamed steel pipe.
On the other hand, a two-color thermometer, which is used to carry out the present invention, picks up two particular wavelength components in visible light emitted from an object, thereby carrying out non-contact measurement of the surface temperature of the object. The two color thermometer can measure a typical temperature within the temperature range in which visible light is emitted, but cannot measure a temperature pattern. Because iron manufacturing and steel manufacturing processes often require the measurement of a temperature pattern, the above described temperature measuring methods cannot easily fulfill such a requirement.